The Transit navigational satellite system is expected to be in operational use during the second half of 1962, though not perhaps with its full quota of four satellites. The system, which will be of considerable significance to both air and surface navigation, is here described by its originators, Dr. Kershner and Dr. Newton, of Johns Hopkins University in the United States. Using a single of the two frequencies transmitted by the satellite, the mean navigation error will be about one mile, limited by refraction. Using both frequencies the mean error will be about ½ mile, limited by the accuracy of the satellite coordinates that will be transmitted. With elaborate equipment, it will be possible to navigate to about 0·1 mile, although the satellite coordinates that will be available to the ordinary user will not reflect this full accuracy. When all four satellites are in orbit, a fix will be available every 110 minutes, on the average, with occasional intervals of 220 minutes between fixes.

The aim of the Duke of Edinburgh's lecture is to extend the horizons J. of navigational interest. I shall try to show how modern scientific methods are greatly increasing our understanding of how the oceans themselves work, and, at the same time, do all I can to maintain that this new knowledge is not just a matter of curiosity. If vigorously developed it will be of much practical use to seamen, and of great benefit to us all. The time is opportune. Scientifically inclined nations recently have been making organized all-round exploration of the human environment. As well as major Antarctic operations, and the rush to Space, there is growing realization that the oceans are coming within our grasp for major technical exploitation.

The main reason for improving the navigation of merchant ships today is economic, determined by factors such as the price of long-shoring and the penalties for late (or early) arrival in port. In this paper, which was presented at an Institute meeting on 13 April 1962, the Assistant Marine Superintendent of the Holland–America Line examines critically the standards of equipment and operation in modern cargo vessels and suggests a whole range of improvements based on experience within his own Company.

Any discussion on the navigational problems of hovercraft must obviously be closely associated with the control characteristics of the craft. Although these machines have been widely publicized as capable of operating over almost any terrain which is reasonably flat, it will be assumed that the present discussion is concerned primarily with operation over water.

The word hovercraft may be regarded as a generic term in the same category as aircraft, ship, motor vehicle &c., and practical examples are likely to take a variety of forms depending upon their particular application. Thus, the control characteristics and the way in which they affect the navigational problem are likely to vary, in degree at least, amongst the different types. Again, it must be realized that the hovercraft as a transport system is only at the beginning of a long development phase, and any remarks of a general nature which are made at this time must be read in that context. Even at this early stage, however, two distinct applications of the hovercraft principle, as applied to over-water transport machines, have emerged and it is important to appreciate the difference between them.

1. Introduction. By definition a hovercraft or air-cushion vehicle is a vehicle capable of being operated so that its weight is partly or wholly supported by a self-generated cushion of air that is dependent for its effectiveness on the proximity of the surface over which the vehicle operates. Thus from the safety aspect of navigation a hovercraft must be treated as a surface vehicle or craft; for any collision risks involved are proportional to the amount of conventional surface vehicles or craft and static obstructions, in the area of operation. The clearance of minor obstacles less than the hoverheight is practicable; but on present experimental craft with an undersurface clearance of three feet, these clearances are limited to small buoys, waterlogged obstructions and rock outcrops of limited height.

The Transit system of navigation is based upon the observation, by radio, of artificial satellites. The basis of the method is to determine the line-of-sight velocity of the satellite towards, or away from, the observer at various times as the satellite moves across the sky. With a knowledge of the corresponding orbital positions and velocities of the satellite, the observations can be used to determine, without ambiguity, the position of the observer.

The Safety of Life at Sea Conference, 1960, recognized the special danger of the concentration of maritime traffic in converging areas and entrusted shipping companies with the responsibility of establishing the channels to be followed in these areas. The three Institutes of Navigation may be helpful to the companies in this respect through the competence and prestige of their special working groups. The problem consists in defining one-way channels and cross-overs for different streams of traffic. In entrusting this responsibility to the companies, the London conference implicitly agreed that the organization of converging areas was a simple application of the International Regulations for Preventing Collisions at Sea to the particular conditions of each area.

In converging areas ships will remain entirely and solely subject to the Collision Regulations. Agreements on the channels to be used will be covered by Rule 29 which refers to the ‘Ordinary Practice of Seamen’.

Beside measuring changes of distance by means of the doppler effect on frequencies transmitted by a satellite, it is possible to observe altitudes and azimuths or the rates of change of these quantities. Advantages and disadvantages of such observations are compared with the Transit programme; the formulae for position lines determined by rates of change of altitude and azimuth are derived and discussed. Measurements of distance, at present feasible only by radar, may be possible in future by comparison of atomic clocks; the evaluation is simpler than for all other observations of satellites.

Four steps to Longitude! If we chose, we might interpret the phrase by a sequence of four names: Ptolemy, Charles II, Tobias Mayer and Nevil Maskelyne—the last in 1763. But in fact the steps represent the four marine timepieces made by John Harrison—familiarly known as H1, H2, H3 and H4 of which the last proved its efficacy in 1762. The longitude was found, and by a ‘machine’, just two centuries ago. Now the bi-centenary is being celebrated by a very elegant and informative exhibition at the National Maritime Museum, Greenwich. No navigator should miss it. Even if he thinks scorn of ‘ancient history’ he owes the inventor of the first English chronometer a tribute of respect.

This paper has been written with the SRN-2 and VA-3 type of craft in mind; they are basically over water craft but with a capability of operating over land for the purpose of embarking or disembarking passengers and freight or of crossing mud flats or sandbanks. Immersed sidewall craft have not been considered since their problems are similar to those of high-speed launches. Overland air-cushion vehicles will, as Mr. Lamb has pointed out, most likely operate over prepared routes and therefore navigation should not present any problems.

The main advantage offered by air-cushion craft is speed. The second advantage is its amphibious capability. Because of this an air-cushion craft can operate routes that are out of the question for any other kind of vehicle except perhaps a helicopter. An example of such a route is the proposed Rhyl–Hoylake ferry, which at low water is almost an overland route.

A revision of the North Atlantic Track Agreement would make it possible to form a larger group of subscribing companies. The existing tracks could be simplified and the danger of convergence on certain channels avoided by modifying the double landfall at Fastnet and Bishop and by moving certain junctions. This could be done without unduly lengthening the channels. One might also replace the concept of fixed channels by the more liberal one of protected channels, which one might call ‘Naviroutes’.

Ships wishing to follow these would benefit from increased safety by the use of certain simple rules, which may be summarized as follows:

A neutral zone, varying in size according to the region, of the blue-line type proposed by Oudet and Poll would separate traffic going in opposite directions. In good visibility ships crossing a ‘Naviroute’ would do so at an angle of more than thirty degrees; in fog ships would cross a ‘Naviroute’ at right angles and at low speed. Each of these rules is dictated by commonsense to every seaman with experience of crossing busy shipping channels.

It has already been explained that one has to correct for the effect of the ionosphere upon the doppler shift in order to track the Transit satellites with sufficient accuracy. At the Radio Research Station, Slough, the converse problem is being investigated; we are looking at the effect of the ionosphere upon the Transit satellite signals in order to find out about the ionosphere itself. In fact the doppler correction term is directly related to one of the quantities of major interest, the electron content of the ionosphere. This is the number of electrons in a unit column up to the satellite height. We are interested in the daily, seasonal and solar variation of this quantity.

The paper examines in particular the possibilities of using leader cables for establishing traffic lanes at sea. A brief history of the leader cable is given, followed by discussion of the components and variables in the system such as the cable itself, the energizing frequency and detection and indicating devices. The application of leader cables in the context of modern navigational conditions is then examined. An appendix gives a valuable list of some of the more important references on leader cables.

The hovercraft will be required to move over land and water and, dependent on siting and the state of the tide, will also move over mixed conditions—land, mud, water, rocks, &c. It is a flexible vehicle and it will be capable of working in many parts of the world, and thought should be given right from the start of development to the use of aids to navigation which are self-contained.

The various weather conditions it will be expected to operate in and to maintain scheduled movement will vary from daylight—fine weather and clear visibility—to night and bad weather.

1. Navigational equipment. The radio navigational equipment likely to be carried in a hovercraft will depend on the type of craft, the route or area of operation, and the economics of operation.

At present the operational requirements for navigational equipment are not fully crystallized because no hovercraft is yet in commercial operation and the operational requirements may well differ from trial requirements. However, two distinct types of hovercraft could become operational soon, the immersed sidewall hovercraft and the amphibious air curtain hovercraft.

The paper discusses the measure of control to be exercised by the Port Authority in a Port Entrance Area where shore radar enables tracks to be made of all ships present. The problem becomes acute where great numbers of ships are trying to enter and leave in restricted visibility, creating danger and confusion.

In a previous paper presented at the conference, Commandant R. Betton, Captain of the Port of Le Havre, suggested that it was perfectly possible for shore-based guidance radars to be used to reduce collision risks at the entrances to harbours, provided this supplementary function is precisely denned in terms of how much authority harbour administrations can exercise over ships outside the harbour. Betton stipulated that any control should only be exercised by experienced seamen and that they should not have the right to interfere in manœuvres for which masters should have sole responsibility.

Training courses on marine radar simulators are held in this country at the Navigation Schools and Colleges in London, South Shields, Hull, Glasgow, Liverpool and Cardiff, with Southampton starting at some future date. The entry for each five-day course is limited to six members and places on the courses are at present generally restricted to serving masters and chief officers. The purpose of these courses is to give seagoing masters and senior officers realistic practice in manœuvring their vessels by radar in conditions of bad visibility without any of the risk involved in an actual encounter between vessels at sea, as well as risk-free opportunity to try out and test the different methods of radar presentation and plotting.

This paper, a shortened version of one presented at the joint meeting of the British, French and German Institutes of Navigation held in Dusseldorf last May, reports work undertaken in Germany on the automatic detection and solution of air collision situations. The work is being carried out jointly at the Berlin Technical University and the Telefunken Company at Constanz, in close consultation with the German air traffic control authorities.